The "erotic services" section will be removed within seven days and will be replaced with a new "adult services" category. Posts in that new section will be "manually reviewed" by Craigslist employees, the company said.

Nude or graphic photos will also be banned from the new adult services section, according to Illinois Attorney General Lisa Madigan.

"It's clear to everyone that Craigslist's erotic services section was nothing more than an Internet brothel," Madigan said in a statement. "I'm encouraged that Craigslist has agreed to fundamentally change how they operate and monitor their site. The steps they're taking are the only effective way to prevent the exploitation of women and children."

Craigslist has come under increasing scrutiny because of several high-profile alleged crimes that have involved the Web site, most recently those of the so-called "Craigslist Killer" who police say targeted women who advertised exotic services on the site.

Madigan, Connecticut Attorney General Richard Blumenthal and Missouri Attorney General Chris Koster met with Craigslist lawyers last week, demanding that the site remove ads they contend are advertisements for illegal sexual activities. The South Carolina attorney general last week also threatened a criminal investigation of Craigslist officials if the site did not remove postings he said were pornographic or encouraged prostitution.

Blumenthal said that Craigslist informed him of the changes Tuesday night. Both Blumenthal's and Madigan's offices said they would continue to monitor the site to make sure ads for prostitution don't migrate to other sections of the site.

"We will be monitoring closely to make sure that this measure is more than a name change from erotic to adult and that the manual blocking is tough and effective to scrub prostitution and pornography," Blumenthal said in a statement.

Not everyone was impressed with the changes. "Several weeks ago, we informed Craigslist of an impending criminal case that implicated its website. Rather than work with this office to prevent further abuses, in the middle of the night, Craigslist took unilateral action which we suspect will prove to be half-baked," New York Attorney General Andrew Cuomo said in a statement.

Cuomo's statement did not make the nature of the pending case clear, but sources close to the investigation said the attorney general's office approached Craigslist several weeks ago to notify the company of investigations into a number of areas, including prostitution rings that advertised on the site.

Cuomo's office, sources said, asked Craiglist not to take down the questionable ads, because they believed the sex for sale services would move to another area. Instead, the office made suggestions to Craigslist on how to track IP addresses and telephone numbers connected to questionable ads and how to monitor repeated use of addresses, phone numbers and credit card accounts by advertisers who used a variety of names, the sources said.